The present invention relates to a vacuum film forming apparatus of the type including a substrate heating unit in a vacuum chamber so as to epitaxially grow a semiconductor film on a substrate.
Many proposals have been hitherto made as to a vacuum film forming apparatus of the foregoing type. For example, a chemical vapor deposition method closely associated with the film forming apparatus including a substrate heater is described in each of the following documents.
U.S. Pat. No. 3,156,591 granted to Arthur P. Hale, et al. to provide a chemical vapor deposition method and titled "Epitaxial growth through silicon dioxide mask in a vacuum vapor deposition process",
Paper published by T. Ohmi, et al. in Applied Physics Letter 52(14) published Apr. 4, 1988 and titled "High-rate growth at low temperatures by free-jet molecular flow: Surface-reaction film-forming technology",
Paper published by K. Fujinaga, et al. in Journal of Vacuum Society B5(6) published Dec. 11, 1987 and titled "Silicon epitaxy on germanium using a SiH.sub.4 low-pressure chemical-vapor deposition process",
Japanese Patent Application Laid-Open No. 257322/1989 titled "Method of producing a semiconductor",
Japanese Patent Application Laid-Open No. 230225/1989 titled "Apparatus for producing a semiconductor", and
Japanese Patent Application Laid-Open No. 230226/1989 titled "Apparatus for producing a semiconductor".
With respect to a conventional gas source epitaxy apparatus including a substrate heater such that a heat source required for heating a substrate is arranged in a vacuum chamber, not only the substrate but also the heat source are exposed to a source gas.
When the substrate is heated in the conventional apparatus as a source gas is introduced into a treatment chamber, the source gas is thermally decomposed on the heat source as well as in the region peripheral to the heat source, whereby a resultant product is produced in a wide region inclusive of the substrate to be treated.
In addition, when a resultant product is deposited on a substrate heating unit, there arise some problems in that the thermal insulating property of the substrate heating unit is degraded, the heater serving as a heat source fails to be turned on, the intensity of heat ray irradiation from the heat source fluctuates, and the uniformity of heat ray irradiation is deteriorated.
Additionally, it has been found that a resultant product deposited on the substrate heating unit and other components leads to a the formation of dust particles, resulting in the rate at which a thin film is formed being reduced undesirably.
Further, another problem is that impurities such as carbon or the like fly from the heater onto the substrate as the heater is heated.